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Team Pins Origins of Dog Domestication in Central Asia

NEW YORK (GenomeWeb) – Dog domestication most likely occurred somewhere in Central Asia, according to a new genetic analysis of purebred dogs and free-roaming village dogs from around the world.

A University of Cornell University-led team did array-based genotyping on almost 5,400 purebred or village dogs, representing 161 pure and mixed breeds from dozens of countries. Based on the genetic diversity and linkage disequilibrium gradient in village dogs in Egypt, India, and Vietnam with little European dog ancestry, the group speculated that dogs were originally domesticated somewhere in and around what is now Nepal and Mongolia.

In the process, the researchers identified regions where village dogs are admixed with dogs of European ancestry, along with parts of the world where dogs were descended from predominantly European or indigenous stocks. Their findings appeared online this week in the Proceedings of the National Academy of Sciences.

"Indigenous dog populations in the Neotropics and South Pacific have been largely replaced by European dogs, whereas those in Africa show varying degrees of European vs. indigenous African ancestry," corresponding author Adam Boyko, a biomedical sciences researcher at Cornell, and his colleagues wrote.

Past work suggests dogs were domesticated from Eurasian gray wolves some time in the past 15,000 years ago or more, Boyko and his co-authors noted. But while mitochondrial and Y chromosome sequence data have placed this domestication somewhere in China, shared mitochondrial haplotypes between ancient wolves and modern European gray wolves, together with archeological evidence, hint at a potential European origin.

To delve deeper into the history of domestication, the researchers decided to draw from genome-wide variant patterns in diverse domestic and village dog breeds. And since purebred dog breeds have been subject to artificial selection and tend to be dominated by European ancestry, they made a point of sampling hundreds of village dogs and local breeds.

After collecting blood samples from free-ranging dogs in 38 countries, the team generated genotyping data at more than 185,000 SNPs — including 360 mitochondrial variants and more than 200 Y chromosome markers — for 549 of the village dogs with a semicustom Illumina CanineHD array.

The researchers used the same array to test 4,676 purebred dogs from 161 breeds, teasing apart indigenous and European ancestry in the dog groups, together with mitochondrial and Y haplotype patterns.

Whereas Vietnamese, Indian, and Egyptian dogs had significant indigenous dog ancestry, for example, dogs from Fiji and French Polynesia had almost exclusively European ancestry, while Papua New Guinean, Solomon Island, and African dogs showed varying degrees of admixture.

Within the village dogs, the team saw elevated genetic diversity compared with the purebred domestic dogs, along with enhanced mitochondrial and Y chromosome diversity in dogs from East Asia, India, and Southwest Asia.

And by folding in linkage disequilibrium data, the researchers concluded that dog domestication likely occurred somewhere in Central Asia, with dogs from nearby locales such as Afghanistan, India, and Vietnam still carrying most of the known dog haplogroups.

Boyko and his co-authors cautioned that "we cannot rule out the possibility that dogs were domesticated elsewhere and subsequently, either through migration or a separate domestication event, arrived and diversified in Central Asia."

"Although it is difficult to explain the clear gradient of short-range [linkage disequilibrium] out of Central Asia if dogs were domesticated from a far-flung region, studies of extant dogs cannot exclude the possibility of earlier domestication events that subsequently died out, or were overwhelmed by more modern populations," they explained.